The International Astronomical Union officially acknowledges 88 constellations, encompassing both the northern and southern celestial hemispheres. Here, we present a selection of the most recognizable constellations found in the northern sky.Aquarius, the water bearer, achieves renown partly due to its place in the zodiac and its association with a popular Broadway song. Nevertheless, it remains relatively inconspicuous in the night sky, making it challenging for many to spot. This constellation plays host to the summer Delta Aquarid meteor shower, which, like Aquarius itself, is characterized by its subtle presence and limited visibility.
Among the constellations belonging to the zodiac, Aquarius shines most brilliantly during the late summer and early autumn evenings, gracefully traversing the southern sky and remaining visible throughout the night. It holds a significant place in the pantheon of ancient constellations, with the Greek astronomer Ptolemy cataloging it nearly two millennia ago. In the contemporary constellation system, it ranks as the tenth-largest among the 88 recognized constellations.
Several of the stars within this constellation bear names that symbolize luck and good fortune. The most notable examples are Sadalmelik and Sadalsuud, the constellation's two brightest stars. These names originate from ancient Arabic and carry the meanings "lucky one of the king" and "luckiest of the lucky." It's possible that these names were chosen due to the stars' positions in the sky. At the time these constellations were named, the sun traversed this region during early spring, marking the end of the long winter nights and the arrival of life-giving rains. Aquarius is just one of the "watery" constellations found in this part of the sky.
Within this constellation lies the globular cluster M2, positioned 38,000 light-years away from Earth. Remarkably, M2 is bright enough to be observed with binoculars, despite its considerable distance. This cluster is composed of approximately 100,000 stars densely packed into a sphere only a few light-years in diameter.
M2 is a relic of the past, being one of the oldest objects within our galaxy. All of its once-bright, massive stars have long since exhausted their nuclear fuel. Today, the brightest stars in M2 are yellow and orange giants—stars that once resembled our Sun but have expanded and brightened as they consumed their core's nuclear fuel. It's worth noting that M2 doesn't belong to the flat disk of the Milky Way galaxy; in fact, the disk didn't even exist when M2 came into existence. Instead, M2 is situated within the galaxy's halo, which is a surrounding shell of stars.
One of the remarkable features within the constellation Aquarius is the relatively unknown star system named Gliese 876. This star system centers around a red dwarf star, which, in contrast to the Sun, is about a third as massive and only emits roughly a thousandth of the Sun's brightness. Consequently, even though it's a mere 15 light-years away, it remains too dim for direct naked-eye observation and necessitates the use of a telescope.
Within this intriguing system, astronomers have identified at least four planets, among which one stands out as potentially one of the most Earth-like worlds ever encountered. Additional evidence supports the notion that this planet is approximately twice the size of Earth and significantly more massive. Similar to our own planet, it likely possesses a rocky composition, and its gravitational force is sufficient to retain any initial atmosphere it may have possessed. However, despite these similarities, this planet is unlikely to harbor life due to its extreme proximity to Gliese 876, resulting in surface temperatures soaring to hundreds of degrees. If life does exist on this planet, it would likely exhibit substantial differences from Earth's life forms.
Aquarius also houses another intriguing system known as K2-138, comprising at least six planets. This system features a cool orange star that closely rivals the Sun in size. Five planets were confidently identified, all residing much closer to their host star than Mercury does to the Sun. Additionally, the project uncovered evidence of a sixth planet, which Kepler could not confirm before its shutdown. However, astronomers subsequently aimed another space telescope at this system, successfully validating the existence of the elusive sixth planet.